100 " pure hydrochloric (muriatic) acid.
20 " potassium chlorate.

All this goes to show you that there is ample liberty of choice as to
processes in etching. It is well to try them all, as it is well to try
every thing that may give new and unknown results, may inspire ideas, or
may lead to progress, neither of which is likely to happen in the
pursuit of mere routine work.

CHAPTER VII.

RECOMMENDATIONS AND AUXILIARY PROCESSES.--ZINK AND STEEL
PLATES.--VARIOUS THEORIES.

A. RECOMMENDATIONS AND AUXILIARY PROCESSES.

73. =The Roulette.=--The latitude which I gave you does not extend to
the point of approving of all material resources without any exception.
There is one which I shall not permit you to make use of, as the needle
has enough resources of its own to be able to do without it. I allude to
the _roulette_, which finds its natural application in other species of
engraving.

74. =The Flat Point.=--Employ the _flat point_ with judgment; it takes
up a great deal of varnish, but gives lines of little depth, and of less
strength than those which can be obtained by prolonged biting, with an
ordinary needle.

75. =The Graver or Burin.=--"And the graver: what do you say to that?"

The graver is the customary and fundamental tool of what is properly
called "line-engraving." Although it is not absolutely necessary in the
species of etching which we are studying, there are cases, nevertheless,
in which it can be used to advantage, but always as an auxiliary only.

If, for instance, you desire to give force to a deeply bitten but
grayish and dull passage, or to a flat tint which looks monotonous, a
few resolute and irregular touches with the graver will do wonders, and
will add warmth and color. A few isolated lines with the graver give
freshness to a muddy, broken, or foxy tint, without increasing its
value.

The graver may also be employed in patching deeply bitten passages.

The graver, of a rectangular form, with an angular cutting edge, is
applied almost horizontally on the bare copper; its handle, rounded
above, flat below, is held in the palm of the hand; the index finger
presses on the steel bar; it is pushed forward, and easily enters the
metal: the degree of pressure applied, and the angle which it makes with
the plate, produces the difference in the engraved lines. The color
obtained by the burin is deeper than that obtained by biting, as it cuts
more deeply into the copper.